1. Field of the Invention
The invention relates to a frictional resistance coupling for the non-rotary and releasable connection of two coaxial components, for example of a hub to a shaft according to the features described in the preamble of claim 1.
2. Description of the Prior Art
A coupling of this type is known from EP-PS 0 178 300 (U.S. Pat. No. 4 616 948). The known coupling comprises an outer part and an inner part, which between them enclose an annular chamber which is conical in the axial direction and is pressure-tight. A symmetrically conical annular piston is arranged to move axially in this annular chamber. The displacement comes about due to the supply of a pressure medium to respectively one of the two end faces of the annular piston, due to which a radial clamping force is exerted for example on the shaft for the transmission of a torque by frictional resistance. The outer part of the known coupling may be constructed either for insertion in the hub of another component or as an independent component attached on its end face for example to an articulated shaft. The fit between the surfaces involved in the frictional resistance must therefore be fixed exactly. In this case, the full torque-transmission capacity between the surfaces involved in the frictional resistance, in particular on the shaft surface, is only possible if the annular piston, during its axial stroke, in conjunction with the conical wall, can produce an adequate radial tension.
The stroke of the annular piston or its position within the annular chamber cannot however be ascertained from outside. It would indeed be conceivable for example to apportion the actuating pressure in the annular chamber so that solely a pre-calculated partial stroke of the annular piston and thus a corresponding radial tension comes about. However, this is too inaccurate with regard to the coefficients of friction which cannot be monitored exactly within the frictional resistance coupling, in particular between the annular piston and the conical wall, and in view of the manufacturing tolerances and is therefore unreliable with regard to establishing the torque of the frictional resistance coupling which can be transmitted.
Therefore the frictional resistance coupling is designed so that the highest radial tension and thus the highest transmissible torque is achieved when the annular piston has completed its full stroke within the annular chamber, the maximum actuating pressure for the displacement of the annular piston always being supplied to one pressure chamber.
It would also be possible theoretically, by measuring the quantity of pressure medium supplied, to ascertain the movement or the position of the piston within the annular chamber. However, on account of leakages at the screwed couplings, the indication tolerances of the measuring device for the pressure medium and the elastic deformations of the components taking part, under high pressure, falsifying the measured value, this measuring method is also not reliable.